Generally, devices for washing the blanket cylinders of a printing press use a washer roller which has been saturated with detergent to clean the blanket cylinder of a printing press. Often, in order to improve this cleaning action, a doctor blade is provided to clean the washer roller by removing excess detergent and particles from the washer roller. In typical prior washers, because of a single control mechanism, the doctor blade may only engage the washer roller concurrent with the washer roller's engagement of the blanket cylinder. Such a washer mechanism is disclosed in DE-3,903,434 wherein the washer roller engagement mechanism supports and connects to the extreme ends of the doctor blade by two linkage arms.
This engagement mechanism presents several disadvantages. First, the lack of independent control of the doctor blade does not allow for engagement of the doctor blade with the washer roller when the device is not washing the blanket cylinder. Independent control is desirous in that the doctor blade might then be engaged to pre-dampen the washer roller before cleaning or to clean the washer roller after use.
Also, the use of only two linkage arms for supporting the ends of the doctor blade causes uneven distribution along the interface of the doctor blade and the washer roller. This has a tendency to permit deformation or deflection of either the roller or doctor blade and uneven wear of both the roller and the blade.